It is well-known in the field of plastic surgery to enlarge the female breast or replace other body organs or structures with prostheses which are surgically implanted therein. With respect to female breasts, in many instances it becomes necessary to remove the entire mammary gland or a substantial portion thereof as a result of cancerous infection or other disease. The surgical removal of the diseased body tissue leaves voids which may be filled by such a prosthetic implant Such implants provide physical support for the surrounding body tissue and organs and in the case of voids near the skin, preserve the outward appearance of the body. When cancerous, pre-cancerous, or damaged tissue is removed, it is often possible to insert the prosthesis to be implanted through the same surgical incision used for removing the tissue. Particularly in the cases where a radical removal of tissue has occurred it is desirable to use a implant for the purpose of restoring the human body to its original normal form. The restoration of the normal appearance of the body has an extremely beneficial physchological effect on post-operative patients, eliminating much of the shock and depression that often follows extensive surgical procedures.
Among the various problems involved in prosthetic implants are those of preserving the natural shape of the body over time after implantation. Some prior art implants comprise an outer layer of sponge material which retains a relatively natural softness and resiliency similar to the replaced body tissue. However, the inherent porosity of such sponge material has also been a source of considerable inconvenience and disappointment because the sponge eventually becomes invaded with connective tissue, sometimes called capsule formation, throughout all or a major portion of the implant. The connective tissue, being fiberous, shrinks as it ages, sometimes called capsular contraction, resulting in the compression of the implant thereby causing the implant to lose both its original size and shape and its original resiliency. Cases are known where shrinkage has been as much as 20 to 30% of the original size. These changes in shape, size and resiliency may be distressing and embarrassing to the patient and are obviously undesirable.
Other prior art prosthesis comprise a smooth outer surface so that there can be no infiltration of the fibroblasts into the surface of the prosthesis. However, it is difficult to obtain anchoring of the prosthesis to the body because of the difficulty of the connective tissue grown thereon to form a satisfactory attachment thereto. Also, these smooth surface prostheses which are covered with a cellular layer which can not become infiltrated by living tissue, but instead, have a more or less external surface which is formed of an impervious material, so that body fluid can and often does accumulate between the prosthesis and the living tissue. This fluid accumulation may be directly or indirectly related to infection in the patient at the site of the fluid accumulation. Also, in severe cases, the infection may cause necrosis of the tissue in the location of the prosthesis.
Another type of breast prosthesis which is known in the art has a smooth surface to which is glued a porous polyurethane foam or Dacron velour material. It has been suggested that these porous surfaces allow the penetration of tissue and fluids from the surrounding tissue. It has also been suggested that such polyurethane coated prosthesis inhibit the problems of capsular contraction. (See U.S. Pat. No. 4,648,880 and Pennisi, Aesth. Plast. Surg. 9:73-77, 1985). These porous surface prostheses are thick and not very compliant, and therefore, in some cases, are difficult to insert beneath the skin with a small surgical incison. As a result, large incisions which cause unsightly scars may be necessary in order to provide a sufficiently large hole for proper insertion. These porous prostheses are also absorbant to bacterial containing body fluids and thus make infection control difficult. In addition, if the porous material is polyurethane foam, there have been a number of reports that the foam disintegrates in the body after a few months causing severe rashes. Also marked foreign body reaction may also be observed with these foam implants. (Plastic and Reconst. Surg. 61, No. 1, 1978.) Rashes have also been known to occur soon after implantation in some instances, possibly as a result of a body reaction to the antibotic solution in which the polyurethane coated prosthesis is dipped prior to implantation.
In the standard process for manufacturing surgical prosthesis, and particularly, mammary implants, a shell of desired thickness is formed having the desired shape for the particular implant and purpose. These shells may be single lumen, multilumen or expandable type prosthesis such a those used for tissue expansion. The shell generally has a circular hole, termed a patch hole. The patch hole is then covered with a patch which is attached thereto using silicone rubber or other similar biocompatible adhesive. The prosthesis is then filled through a small fill hole with saline, gel, foam, combinations of these materials or other suitable material known in the art and the fill hole is sealed. The prosthesis, having a smooth exterior, is then sterilized and implanted, or it may be covered with a foam material as described above prior to sterilization and implantation.
The above-described problems are overcome by the present invention which is described briefly below.